Brake with soft steel return spring



Mw I, 1956 c. E. BRICKER 2,743,790

BRAKE WITH SOFT STEEL RETURN SPRING Filed March 2'?, 1955 FIG. I

OTI

PULLED OUT TO ORIGINAL SIZE FIG. 2 INVENTOR.

CARL E. BRICKER ATTORN EY United States Patent O l p 2,743,790 BRAKEWITH soET STEEL RETURN SPRING Carl E. `Bricker, Akron, Ohio, assignor,by mesne assignments, to The Goodyear Tire & Rubber Company, acorporation of Ohio Application March 27, 195s, serial No. 344,963 sclaims. (c1. 18s- 152) This invention relates to brakes, especially tospot type brakes, and it particularly relates to a brake of such typewhich has a soft steel return spring therein.

In brake` constructions, suitable means are provided for energizing thebrakes to `force a brake lining into contact with the braking surface,such as a brake disk. The brake also may include some type of means forretracting the brake lining and associated actuation apparatus into aretracted or inoperative position where the brake lining is out ofcontact with the braking surface. Various return mechanisms have beenprovided for automatically positioning thebrake lining in inoperativeposition and the problem of positioning the brake lining in desiredspaced relationship to the braking surface is complicated by virtue ofthe `fact that initially the block of brake lining is quite thick, suchas one-half inch or more, whereas it may be desired to wear such brakelining block down to a thickness of 3A@ inch or less before it isreplaced with a new block. Also, it is very desirable that the brakelining block be positioned immediately adjacent the braking surface whenthe brake lining block and associated means are inoperative so that uponthe instant of brake actuation, the brake lining block must move but avery short distance before it is brought into operative engagement witha braking surface. In order to achieve a desired type of a control uponbrake block positioning means in spot type brakes to position thebraking means in desired inoperative positions, various rathercomplicated controls have been developed, and these controls arerelatively costly to construct and to assemble. Also, the previouscontrols may require some maintenance when in use, or the control mayeven become inoperative due to mechanical failure.

It is therefore the general object of the present invention to provide anew and improved positioning means in a brake, which means comprises areturn spring ccnstructed and arranged to provide an automatic return ofthe braking means to a clearance or inoperative position upon brakerelease and by the spring taking a permanent set as brake lining blockwear occurs and the spring is relatively greatly compressed withrelation to its original size but with the spring having some returnresistance even after taking a permanent set.

Another object of the invention is to use a soft steel return spring inabrake, which spring has a low carbon content and which has no hardeningalloys therein so that the spring has a relatively low yield point andtakes a permanent set readily as compression of the spring occurs.

Another object of the invention is to provide a relatively inexpensive,uncomplicated construction in brakes for returning a brake lining blockto a small clearance inoperative position automatically upon brakerelease.

Yet a further object of the invention is to provide a brake returnspring which can be compressed by increments to a relatively greatcompression with relation to the original spring length and to take apermanent set several dierent times at various compression points, but

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which spring can be pulled out to substantially its original length andbeused for further progressive compression and permanent set cycles.

The foregoing and other objects and advantages of the invention will bemade more apparent as the specification proceeds.

The present invention relates to a brake assembly comprising a brakelining block, a brake dise, a cylinder, a piston slidably received inthe cylinder and secured to the brake lining block, and pressure meansfor forcing the piston along the cylinder to bring the brake liningblock into contact with the brake disc. A soft steel return spring iscompressed between the piston and a cylinder end for moving the pistonback into the cylinder a short distance when the pressure means arereleased, which short return movement occurs even after the brake liningblock has been reduced in size appreciably from its original thickness,and the return spring has taken a permanent set from its originallength.

In the accompanying drawings, one embodiment of the principles of theinvention is shown and the drawings comprise:

Fig. l which is a fragmentary vertical section of a wheel and brakeassembly of the invention; and

Fig. 2 which is a diagram of an operative cycle of the spring of theinvention.

In the accompanying drawing and specification, corresponding numeralsare used to refer to corresponding parts to facilitate comparisonbetween the specification and drawings.

Reference now is directed to the details of the structure shown in thedrawings and a brake is indicated as a whole by the numeral 1. Thisbrake 1 has a brake housing 2 that is suitably secured to a fixedsupport means, such as an axle 3. The brake 1 is used in combinationwith a conventional wheel 4 which is journalled on a bearing 5 carriedby the axle 3. The wheel 4 carries a brake disc 6 which is engaged withthe wheel 4 for rotation therewith by conventional means such asa numberof axially directed keys 7 that are secured to the wheel 4 by cap screws8. The brake disc 6 is conventionally positioned for movement in adirection axially of the brake 1 only by the keys 7 engaging slots inthe periphery of the brake disc 6 so that the brake disc can moveaxially as brake lining block Wear occurs. The brake housing 2 positionssubstantially conventional spot type of braking means therein so that atleast one axially directed cylinder 9 is formed in the brake housing 2and a piston 10 is slidably received in the cylinder 9. The piston 10 issealed with relation to the cylinder by conventional sealing means, suchas an O-ring 11.

The drawing shows one brake lining block 12 which is iixedly secured tothe brake housing 2 adjacent a side face of the brake disc 6 by suitablemeans (not shown), While a second brake lining block 13 is movablypositioned on the opposite side of the brake disc 6. Usually the brakelining block 13 has a metal disc 14 on a face thereof and suitable means(not shown) secure the brake lining block 13 and metal disc 14 to thepiston 10 for movement therewith.

The open end of the cylinder 9 is closed by conventional means, as by anend cap 15 that is retained in place by a lock ring 16. An O-ring, orsimilar sealing member, is carried by the end cap 15 to seal it in thecylinder 9. Thus any suitable brake actuating means may provide liquidunder pressure intermediate the inner surface of the end cap 1S and theadjacent surface of the piston 10 to produce movement of the pistontowards the brake disc 6 in order to achieve a braking action at desiredtimes.

The axially inward movement of the piston 10 forces the brake liningblock 13 against the brake disc 6 and moves-the-brakedisc axiallylinorder to bring the opposed.l face. ,.of.. the., brake. disc.. into.braking. engagement with the xedly positioned brake lining block 12.After brake actuation, it is necessary that a suitable operativeclearancebeprovidedgim thef brake 1 and to this end asimplefbutheiective construction isV providedy by the invention. Thus asoft steel returnfspring- 18 is positioned intermediate ashoulderl 191formediat an end of the cyl inder- 94J and a shoulder 20` provided' onthe axially inner surface of the piston 10. The brake returnspring18"wi1l becompressed on= movement ofL the piston 1li towards-the brakedisc 6g andthe spring, when braking'forces"are-released; will move thepiston lll-and as sociated `meanssli'ghtly axiallyv outwardly of thebrake in'order to provide the-f desired small operative clearance in thebrake;

It-A is, an importantv4 feature off theinvention that the return springofithe invention has a composition that is slow to work harden', andwhich takes a permanent set at'a relatively low stressl when the springlis distorted, but with' the spring being of a nature `thatit still wouldhave a slight return spring action afterbeing stressed past its yield,point, in order to provide they clearance required'in the brakeforoperation. Thereturn spring naturally is free from any hardeningalloys. Another important feature of the soft steel return spring isthat after it has gone through a complete compression cycle in whichit'has taken a new permanent set several times as the original'relatively thick brake lining blocks 12 and 13 are. worn down to aminimum thickness, the softsteel return spring 18'can be stretched outto substantiallyJits original length and have another operative cycleand this stretching out and re-use of the spring can beY repeatedseveraly times before the spring would break or be otherwise renderedinoperable. It will be realizedJ that almost any type of a steel springcould be used for. onecompression cycle if it has been satisfactorilyannealed to give the spring a relatively low yield point.

The action ofV thesteel spring of the invention is that of any steelpartwhenthe material is stressed beyond itsv yield point,4 as the originallmaterial inherently has a small. amountof spring-back from the stressedposition to` which the material has been moved. However, the springtakes. ak permanent set on yrelatively low compressionk andfthe, returnmovement of the spring is only a small fraction, oftheoriginalamount ofcompression of `the spring requiredto distort it beyond its yield point.

While any suitable material can be usedto make the returnspring 18;usually steel is the material used as othermaterialsare took low inmodulus. One material for the-,spring that gave excellent results in thepractice of the invention is aY dead soft Armco iron which had .Ol to.03 carbon content, while: plain carbon steel No. 1005; also gavekgood,y results-when used as a material for makingjthe. returnspringjf18.

Fig.y 2 of, the drawings shows diagrammatically in exaggeratedrformntheinitial length ofthe returnv spring 18, .itsglengthfA when loaded;itsinitial yield point, `return from; initial yield point, etc. Thisillustrative cycle shows.that,.for example, a springmight have threedifferentyield pointsfasrit is` compressed and thus take three new andprogressively shorter released lengths as the, brakeflining:` blockswear sol the, return spring is progressively compressed but functionstoprovide a desired` small, operative-clearance when the brake isreleased; Thespring` 18 of 'the drawing is made to the lengthdesignated: Formeel Where' the brake clearance is normal engagementl ofthe brake will compress the spring to the dimensionzdesignated LoadedShould Wear of the brake occurA to such an extent that the brake bloclcvmust movea distance greater than the normal clearance to a positionindicated by the first Yield Pointip'reading downwardly.otf'Fig.y 2;thespring would take enough permanent set as merely to recoverto the Theresultwould, be,that.

length marked Recovery the brake block is' returned by the spring alesser distance and the normal clearance therefore reestablished.r`hereafter, the spring operates to return the brake block untiladditional wear of the block permits the spring to be compressed to thesecond Yield Point. Thus pro gressive shortening the spring occurs andautomatic clearance adjustment isi attained. y lActually@ thel spring inoperation would have almostanl'innte, number.- of 2 new released lengthsasitwouldttake'a new Aset,e'.ve1ty simple but inexpensive type of areturn spring has been'- provided in the novelbrake of the inventionand'thatl the construction providedwill eiectively'function--to providethe desired operating clearances-in thelbrake; butU yet will permit themovement'of brake-linings"-axiallyfof4 the brake'as lining wear occursso that'thebrake lining-V blocks can be maintained in desired? close"relationship'A to a brake disc for braking action; ThusY it is thought"that the objects of the invention'are-achieved.

While a certain representativeembodiment'and details have been shown forthe purpose of illustrating theinvention, it will be apparent to thoseskilled in'this art that various changesandmodifications maybe made;

therein without departing from the spiritor scope of the invention.

l. Brake mechanism for applyingva deceleratingforce to a rotatablebrakingsurface, saidmechanism compris'- ing a block of material opposedto the rotatable surface and normally spaced. therefrom, support meansretaining said block against movement inthe direction of' rotation ofsaid surface while permitting movement toward said surface, block-movingmeans for moving said block from a retracted positionjinto frictionalengagement with said rotating surface, said blockhaving an expendiblebrake liningv subjected to wear. by such frictional engagementandlthereby reducing the dimension of said block, and a metallicspringmounted be.-

tween said support and saidblock inopposed compressed. relation to saidblock-moving means and. arrangedY to..

hold said block in its retractedposition, withthelining out ofengagement with saidrotatable surface by. a'

determinate space independent of such wear, said spring being ofmaterial having such4 elastic propertiesas totake permanent set whencompressed by movementA of said block toward said brakingsurface over. adis-iv tance exceedingthe determinate clearance space there.-A

between but to fully recover fromV compressivev movement not exceedingsuch determinate clearance'spaee;

2. Brake mechanism for applyingfadecelerating force to a rotatablebraking; surface, saidz mechanism; comprising a block ofmaterialtopposedrto: the rotatable ,surf face and normally spacedtherefronnsupport mearlsxefy tain said block against movement in`thevdirection of'rror..

tation of` said surface while permitting i.. movement-,to-

ward said surface, block-moving means for movinglsaid block from aretracted position into" frictionalfengagement with said rotatingsurface, said`- block havinganexpendible brake lining subjected toiwearby suchfric-A tional engagement andv thereby reducing'the dimension ofsaid block, and a metallic springmounted'between said support and. saidblock in opposed compressed'y re-1 lation to saidblock-moving means andarranged to holdsaid block in its retractedposition with the lining`outrot;`

Having thus described my invention, what. is claimed".

engagement with said rotatable surface by a determinate spaceindependent of such Wear, said spring being of material having a limitof elasticity at an amount of distortion incident to movement of saidspring under force of said block-moving means exceeding the normalmovement necessary to close said space.

3. Brake mechanism for applying a decelerating force to a rotatablebraking surface, said mechanism comprsing a block of material opposed tothe rotatable surface and normally spaced therefrom, support meansretaining said block against movement in the direction of rotation ofsaid surface while permitting movement toward said surface, block-movingmeans for moving said block from a retracted position into frictionalengagement with said rotating surface, said block having an expendiblebrake lining subjected to wear by such frictional engagement and therebyreducing the dimension of said block, and a metallic spring mountedbetween said support and said block in opposed compressed relation tosaid block-moving means and arranged to hold said block in its retractedposition with the lining out of engagement with said rotatable surface,said spring being of material providing elasticity of the spring withinnormal distortion under force closing said spring by a determinateamount in closing said space and exceeding the yield point whendistorted by movement exceeding such space.

References Cited inthe le of this patent UNITED STATES PATENTS 2,392,970Bricker Jan. l5, 1946 2,503,755 Martin et al Apr. ll, 1950 2,556,976Oetzel June 12, 1951 2,631,840 Bugenhagen Mar. 17, 1953 2,644,549 CagleJuly 7, 1953

